1. Field of the Invention
The present invention is directed towards a new and improved multiple thrust range, live loaded packing system for a valve stem and for a valve employing such system so that at least two ranges of thrust values may be provided to exert a live load on a packing ring around the valve stem. The packing system also provides a means to determine if the preferred or prescribed thrust values are being applied.
2. Background of the Prior Art
Over the years, a wide variety of piston rod packing systems, stuffing box sealing systems, valve stem sealing and piston ring sealing systems have been developed and some of these systems have utilized a live load thrust against a packing member to facilitate sealing around the piston rod or valve stem. U.S. Pat. No. 601,614 to Dudley; U.S. Pat. No. 3,659,862 to Sebastian; U.S. Pat. No. 3,713,660 to Luthe; U.S. Pat. No. 3,968,970 to Vogeli; U.S. Pat. No. 4,582,329 to Stalph; U.S. Pat. No. 4,722,507 to Lindackers et al. and U.S. Pat. No. 5,056,757 to Wood, disclose packing or stuffing box systems in accordance with the prior art.
Additionally, the following U.S. patents disclose various configurations of packing systems, valves and specialized live loading packing arrangements for rotary shafts and stems:
______________________________________ Platts et al. 534,575 Platts et al. 548,089 Jacobsen 2,441,705 Astill et al. 3,787,060 Hansen 4,061,157 Francart, Jr. 4,745,944 Lephilibest 4,773,442 Suggs 5,024,453 Wood et al. 5,129,625 ______________________________________
However, none of the aforementioned patents appear to disclose a live loaded valve or stem packing arrangement wherein the simple reversal of one or more components results in a packing system having multiple ranges of thrust value capability.